
function Item(){
}
Item.computeItemCount=function(itemInfo,num){
    var itemCount=itemInfo.get('count');
    itemCount+=num;
    itemInfo.set('count',itemCount)
    return  itemInfo
}
Item.computeCostPrice=function(itemInfo){
    var costPrice= itemInfo.get('count')*itemInfo.get('price');
    itemInfo.set('costPrice',costPrice);
    return itemInfo
}